Material selection for the development and fabrication of structures involves any number of considerations. For example, the use of metals offers obvious benefits in strength while the use of plastics offers equally attractive benefits in moldability and lack of conductivity. However it is also well recognized that any materials also necessarily carry design limitations. For example, metals are obviously quite heavy and may not be suitable for weight-constrained applications, while plastics may not be suitable for applications requiring rigidity and durability. Researchers have long been interested in developing approaches to bring metals and plastics together into a structure or application.
U.S. Pat. No. 5,085,722 provides a composite material of a flat metal substrate with a number of apertures, with plastic material and reinforcing fibers that attach to the metal through these apertures. The composite is described as having greater fracture resistance and impact strength than the non-metallic material alone, while also limiting the transmission of temperature effects through the composite versus what would be experienced if only metal were used.
U.S. Pat. No. 4,569,865 discloses light weight, corrosion resistant automotive bumpers including thin metal outer shells bonded to rigid but resilient foamed plastic cores. An intermediate primer layer preferably of ethylene copolymer is used in the bonding process. The metal is preferably stainless steel or aluminum. Because no bolts are used, the metal layer offers superior corrosion resistance and a smooth appearance.
U.S. Pat. No. 4,682,809 describes a body construction for lightweight passenger vehicles including an elongated shell of highly impact resistant plastics material. A metal chassis is secured to this shell to form an integrated composite structure. This construction offers improved rigidity for body constructions of battery-powered vehicles.
While each of the above approaches may be of interest in their respective selected applications, they are not readily adaptable to a wide range of uses. For example, each requires reinforcing fibers or foamed materials or is limited in scope to large shell-type applications. These and other teachings are generally representative of the techniques and constraints evidenced to date in developing structures of this variety.
There is a need therefore for an integral structure of metal and plastic, in which the plastic is firmly secured to the metal and can nevertheless be injection molded using conventional molding techniques and without requiring special processing.
An object of the instant invention is to provide useful integral structures of metal and plastic in which the materials are effectively joined to form rigid and durable assemblies. A further object of the instant invention is to provide such structures whereby the designer can incorporate plastic ribs to provide further support as may be required for particular applications. A feature of the instant invention resides in the variety of shapes that can be fashioned using the approaches described herein, and with them the number of applications for which this invention is suitable. An advantage of the instant invention is the range of materials that may be selected and suitable for forming integral structures therefrom.
These and other objects, features, and advantages will become better understood upon having reference to the following description of the invention.